Principal Investigator/Program Director: French, Kevin J. Abstract: The long-term goal of this program is to develop inhibitors of human sphingosine kinase (SK) that are effective as therapeutic agents. Because of its critical role in sphingolipid metabolism, we have focused on SK as an innovative molecular target for the development of new drugs for the treatment of atherosclerosis. Sphingolipids are being increasingly recognized as key mediators of cell proliferation, apoptosis and differentiation. In particular, SK is a critical regulator of vascular smooth muscle, endothelial cells, and inflammatory cells that are of central importance in atherosclerosis. Therefore, we hypothesize that SK is a key molecular target for the development of new anti-atherosclerotic drugs. In spite of accumulating evidence for a pivotal role of SK in the regulation of vascular inflammatory processes, pharmacological inhibition of SK is an untested means of preventing and/or treating atherosclerosis. This is largely due to the heretofore lack of pharmacologically useful SK inhibitors. To overcome this problem, we have recently identified novel inhibitors of human SK. These compounds are more potent than any other known SK inhibitor, and do not compete for the ATP binding site of the enzyme. We hypothesize that these SK inhibitors can be used to attenuate the atherosclerotic process, and will conduct the following proof-of-principle studies during Phase I of this project: 1). To determine the in vitro effects of these SK inhibitors on signaling cascades that contribute to atherosclerosis. Each SK inhibitor will be tested in several mechanism-based assays including: proliferation, apoptosis, sphingosine 1-phosphate generation, and induction of adhesion molecules. 2). To evaluate the therapeutic efficacies of SK inhibitors in a rodent model of atherosclerosis. The apoE-deficient mouse will be used as a model for atherosclerosis. Each SK inhibitor will be tested for efficacy in reducing aortic lesions, and effects on circulating inflammatory cytokines and sphingolipids. [unreadable] [unreadable] [unreadable]